Electrical power cogeneration system

ABSTRACT

A cogeneration system includes an engine, a motor/generator unit (MGU) powered by the engine, a compressor powered by the MGU, and a heat storage tank. The system further includes an engine coolant loop which places the engine in thermal communication with the tank, and a vapor loop which circulates refrigerant from the compressor. An air handler unit exchanges heat between the engine coolant loop and the vapor loop. A controller is configured to control the engine, MGU, compressor, and air handler unit, alone or in combination, to heat or cool air supplied to a building and water in the tank, and to selectively charge at least one auxiliary device such as a battery of an electric vehicle (EV) via the MGU. The system may include two power plants, with one, e.g., an EV or a portable module, having the engine and a first engine coolant loop.

TECHNICAL FIELD

The present disclosure relates to an electrical power cogenerationsystem, i.e., a system which uses different energy sources toelectrically power multiple subsystems.

BACKGROUND

Cogeneration may be used to improve the efficiency of various electricalsubsystems, such as the variety of electrically-powered devices used ina typical home or commercial building. Efficiency improvement is gainedby capturing and using the waste heat from the generation of requiredelectricity. That is, a portion of the energy in any fuel used toprovide heat to a home or building is diverted by an engine andgenerator into the production of electricity. For example, one may usean internal combustion engine and an electric generator to generate aportion of the electrical energy required to power a building and usethe heat produced by the engine to heat the building. The remainder ofthe required electrical energy can be provided by connecting to theelectrical grid, or by other devices such as a windmill, solar voltaicpanels, and so on. Likewise, the remainder of the required heatingenergy can be provided by other devices such as solar thermal panels.

Use of a cogeneration system allows a user to produce at least some oftheir own electrical energy on-site. This may be a particularlyattractive option to electricity users residing or working in remotelocations, or in geographic areas that are relatively susceptible toperiodic blackouts or brownouts. Other electricity users may beapprehensive about relying on a single energy supplier for reasons ofelectricity cost. In areas that consume energy generated primarily viacoal-burning power plants, the use of a cogeneration system can help toreduce the level of carbon dioxide emissions relative to exclusive useof electrical power supplied from the grid.

SUMMARY

A cogeneration system is disclosed herein. In its various embodiments,the present system selectively diverts otherwise wasted fuel heat energyfrom a large gas-consuming engine, for instance an internal combustionengine or a fuel cell, to other beneficial uses. Such uses may includethe charging of a battery module. In some embodiments, such a batterymodule may have a high-voltage energy storage system (ESS) of the typeused to power an electric traction motor of an electric vehicle (EV).The charging function of an EV, an extended-range EV, or a plug-inhybrid electric vehicle (PHEV) battery is ordinarily accomplished byconnection to the electrical grid when the vehicle is idle.

The power load of a typical EV battery exceeds by several times theoutput of a conventional cogeneration system. Such systems areordinarily sized on the order of approximately 1 kW of electrical outputto meet the heating needs and some of the total electrical needs for anordinary house, but an EV battery may customarily be charged at powerlevels of between approximately 3 kW and 7 kW or more. The limitedcapacity and various other design limitations of conventionalcogeneration systems can limit the types of functions that can besupported.

Other non-EV support scenarios can present power loads comparable tothat of an EV battery. For instance, a household may simultaneously usemultiple televisions, hair dryers, microwave ovens, and/or otherhigh-wattage appliances at various times in a typical day. Central airconditioning is another relatively large electrical load. Homes relyingon conventional cogeneration systems with a capacity of approximately 1kW or less therefore must still rely heavily on grid energy during timesof peak electrical use.

In the present system, a non-diverted energy stream is used for heatingthe air and/or water supply of a building. Instead of being consumed ina furnace burner, fuel is consumed by a heat engine. The heat engineconverts some of the fuel into heat for heating for the building, butalso diverts some of the fuel into producing mechanical power. Invarious example embodiments, and as noted above, the engine may be alarge natural gas/propane gas internal combustion engine or a fuel cell.The engine delivers its waste heat to the building as needed to providesubstantially all of the required space heating and water heatingfunctions in the building.

In addition, the engine may be used to selectively charge an EV batteryor for other purposes, such as for powering central air conditioningfunctions in the building. Only the amount of energy that is actuallyconverted into useful work is diverted out of the overall energy stream.In other words, the amount of extra fuel that is fed into the engineabove a threshold level required for climate control of the buildingequals the energy value of any useful work, thus providing a nearly 100%efficient process.

In particular, a cogeneration system as disclosed herein includes a gasengine, a motor/generator unit (MGU), and a compressor positioned inseries with the MGU. The system also includes a coolant loop, a heatstorage/hot water tank in communication with the engine via the coolantloop, and a vapor loop for heating or cooling air within the building.The latter function can provide central air conditioning and an optionalheat pump function for a building as explained herein.

A controller is in electrical communication with the engine, the MGU,and the compressor. The controller is configured to control operatingstates of the engine, the MGU, the compressor, and one or more heatexchangers, pumps, clutches, and/or other components of the system,either alone or in combination, in order to heat or cool a supply of airin the building and/or the water contained in the hot water tank. Thesame controller can selectively charge an auxiliary device, e.g., abattery, via the MGU, which in turn may be selectively powered by theengine.

The central air conditioning function may be run directly via the engineusing a natural gas or propane line, or it may be powered from the grid,whichever energy source is more efficient, more readily available, orless costly. For instance, the central air conditioning may be run bythe engine during those times when demands on the electrical grid wouldotherwise exceed its capacity or when electricity prices are high.Relative efficiency or availability may be determined by the controlleror signaled to the controller from an outside source of information. Anoptional geothermal heat sink/underground thermal well may be used aspart of the vapor loop for optimized central air conditioning/heatingfunctionality. For instance, waste heat can be stored underground tobring the average temperature below ground closer to the targettemperature for the building in cold climates. Such an option may bebeneficial when electrical power demands are low and thereforesufficient waste heat is not available.

The system and controller may be optionally configured to keep thebuilding “grid-neutral” for as much of its total operating time aspossible, i.e., using zero or near zero levels of electrical energy fromthe main electrical grid. In such an embodiment, the controller may usea current sensor to detect the incoming current from the grid to thebuilding. The controller may thereafter control the various componentsof the system in a closed feedback loop in response to thisdetected/measured current to drive grid use by the building toward zero.Optionally, the controller may be configured to sense when control ofthe voltage in the building down to a minimum level cannot prevent powerflow to the grid, which may be taken as a signal of grid power failure.In this instance, the controller can act to physically disconnect thebuilding from the grid.

In various embodiments, the engine may be part of the power plant of thebuilding, or it may be located in a vehicle or portable module. Whenused as part of the vehicle or module, a pair of conductive plates maybe used to conduct waste heat to the building from the vehicle/module.One plate may be positioned at the underside of the vehicle and anotherplate positioned externally with respect to the vehicle, e.g., on oralong the ground. When the vehicle is parked, heat may be transferred tothe second plate from the first plate.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a cogeneration system according toa first example embodiment, wherein the components of the system residewithin a building.

FIG. 2 is a schematic illustration of a cogeneration system according toa second example embodiment, wherein some of the components of thesystem reside aboard an electric vehicle.

FIG. 3 is a schematic illustration of a cogeneration system according toa third example embodiment, wherein some of the components of the systemreside aboard a portable module.

DESCRIPTION

Referring to the drawings, wherein like reference numbers correspond tolike or similar components throughout the several figures, acogeneration system 10 is shown schematically in FIG. 1. The system 10and its various embodiments, examples of which are described below withreference to FIGS. 2 and 3, provides for optimal on-site energygeneration. The system 10 may be configured to render an associatedbuilding 11 “grid-neutral” by generating as much electrical energyon-site as the building 11 itself and any accessory devices, such as abattery of an electrical vehicle (EV) 40, might otherwise consume, orproviding sufficient energy back into the main electrical grid shouldexcess capacity be present. The system 10 is sufficiently sized to heatand cool the building 11. Thus, substantial capacity exists fordiverting a portion of any energy stream within the system 10 to theperformance of other useful work tasks, such as but not necessarilylimited to the electrical charging of a battery of the EV 40.

The present cogeneration system 10 includes an engine 12, amotor/generator unit (MGU) 14, and a compressor 16. The compressor 16 isconnected in series with the MGU 14 either selectively or continuouslydepending on the embodiment. In the particular embodiment shown in FIG.1, the engine 12 is integrated into a fixed heating plant (i.e., thebuilding 11). The engine 12 is configured to provide substantially allof the required space heating and central air conditioning for thebuilding 11, as well as any required heating of a volume of watercontained within a hot water tank 24.

That is, heat from circulating engine coolant in an engine coolant loop18 and engine exhaust can be recovered to heat the water in the hotwater tank 24. Heat from the engine 12 and/or from the hot water tank 24can then be used as needed for any desired space heating, such as spaceheating of living or working space within the building 11. Thisparticular configuration effectively replaces a conventional furnace andhot water heater of the type used in most modern homes and commercialbuildings.

The engine 12 may be fed by a gas supply (arrow 44), e.g., natural gasfrom a main gas line, compressed natural gas (CNG) from a pressurizedfuel tank (not shown), liquid propane gas (LPG) from a pressurized tank(not shown), etc. An intake silencer 17 may be positioned with respectto the engine 12 and configured to draw intake air (arrow 19) into theengine 12. A catalytic converter 20 and a heat exchanger 22 (exhaustcondenser) may be used to purify the exhaust stream discharged from theengine 12, while the heat exchanger 22 also increases the amount ofwaste heat recovered from the exhaust 42.

Purified exhaust (arrow 42) can be allowed to escape from the building11 to the outside of the building 11. The piping of purified exhaust(arrow 42) in the various Figures is simplified for illustrativeclarity. In actual use, such purified exhaust (arrow 42) should beplumbed away from the building 11, e.g., via pipes or stacks orientedaway from any possible entry points to the building 11 such as windowsor doors. Water condensed from the exhaust stream can be discharged to asump or waste water collector (not shown). Likewise, the various exhaustsystem elements shown in FIG. 1 are merely schematic. One of ordinaryskill in the art will appreciate that the actual piping configurationmay differ, and that the system 10 may include other elements not shownhere, such as particle filters, selective reduction catalysts, valves,flow meters, pressure regulators, etc.

In different embodiments, the engine 12 may be an internal combustionengine powered by the gas supply 44 in the form of natural gas, propane,or another suitable fuel, or the engine 12 may be a fuel cell, or acombination of fuel cell and fuel reformer. Non-limiting examples offuel cells include a molten carbonate fuel cell and solid oxide fuelcell, both of which are capable of operating at high temperaturesdirectly using natural gas as fuel. A fuel cell can operate well abovethe temperatures necessary for providing cost-efficient heat transferfor space and water heating of the building 11. A fuel cell produceselectricity, but typically consumes mechanical power to operate somecomponents of the engine 12. Thus, the MGU 14, when used in a systemwith a fuel cell engine 12, would need to function only as a motor andnot as a generator.

The engine 12 is in communication with the hot water tank 24 via theengine coolant loop 18. A part of the engine coolant loop 18 may beembodied as a loop of pipe or tubing which conducts heated enginecoolant from the engine 12 to/from the hot water tank 24 as needed, asindicated in FIG. 1 by arrow 21. Example coolants include waterpropylene glycol (WPG) and water ethyl alcohol (WEA), although anysuitable fluid having the desired characteristics may be used. A pump 31may be used in the engine coolant loop 18 to help circulate coolant withrespect to the engine 12.

A thermostatic mixing valve 46 may be used to blend hot and cold waterat the outlet of the hot water tank 24, and thus ensure delivery of hotwater to various points of use within the building 11 within a regulatedtemperature range. This occurs even though the temperature of the waterwithin the hot water tank 24 varies above the customary temperature forhot water along with the amount of heat energy stored within the tank24. For example, the water in the hot water tank 24 may vary intemperature from 45° C., a minimum temperature for hot water, to 85° C.,a normal operating temperature of the engine coolant loop 18, but thethermostatic mixing valve 46 may regulate its output to the buildingbetween 45° C. and 50° C. at all times by mixing cold water with waterfrom the tank when the water in the tank exceeds 50° C.

Still referring to FIG. 1, the hot water tank 24, once it has beencharged with heat via the engine 12, can provide its excess capacity orwaste heat back into the building 11 as needed, e.g., for space heatingof the air in the building 11. Space heating provided by the enginecoolant loop 18 may be optimized via an air handler unit 26. The airhandler unit 26 may be equipped for air input from within the building11 and optionally from the outside. Likewise, the air handler unit 26may be equipped for air output to the building 11 and optionally to theoutside.

The air handler unit 26 may include one or more heat exchangers thereinso as to provide air flow across the vapor loop 25 and across the enginecoolant loop 18. An additional heat exchanger is representedschematically in FIG. 1 as air handler unit extension 126 and shown inphantom. For instance, two heat exchangers in air handler unit 26 andits extension 126 may be used separately, with the air handler unit 26transferring heat (arrows 47) between the air inside of the building 11and the vapor loop 25 and the air handler unit extension 126 exchangingheat (arrows 147) between the engine coolant loop 18 and the air outsideof the building 11. Alternately, the two heat exchangers in air handlerunit 26 and its extension 126 may transfer heat from both the vapor loop25 and the engine coolant loop 18 to the air inside of the building 11.

Alternatively, a heat exchanger 122 as shown in phantom can be usedbetween the loops 18 and 25 (arrow 247). In this instance, enginecoolant can be excluded from the air handler unit 26. Air handler unit126 is omitted in such an embodiment. Ideally, the number of heatexchangers used within the system 10 should be kept at a minimum, andthis circulation and heat transfer within the air hander unit 26 is analternative to providing a separate heat exchanger 122, an example ofwhich is shown in phantom, between the engine coolant loop 18 and thevapor loop 25. This heat exchanger 122 can be positioned at one or moreplaces along the vapor loop 25, for instance as shown, for the mostefficient transfer of heat from the engine coolant loop 18 to the air inthe building 11, or (not shown) between the compressor 16 and a heatexchanger outside the building 11, such as a heat sink or thermal well28.

If the air handler unit 26 is used to provide an air stream from thebuilding 11, through the vapor loop 25, and back to the building 11 andanother air stream from the ambient outside of the building, through theengine coolant loop 18, and back to the ambient outside again, thatoption serves as a way to continue to run the engine 12 when the hotwater tank 24 is fully charged with heat. This may be particularlyadvantageous on particularly hot, humid days when central airconditioning use is the dominant energy consumer in the building 11, inwhich case the engine 12 may be running to drive the compressor 16 so asto provide air conditioning using the vapor loop 25.

The compressor 16 of FIG. 1 can be operated or powered by the engine 12to help remove heat from the air handler unit 26. The compressor 16moves pressurized fluid within the vapor loop 25. The compressor cycleand resultant movement of fluid within the vapor loop 25 ultimatelypulls heat from the air within the building 11, as is well understood inthe art. The vapor loop 25 may contain a refrigerant vapor thatcondenses into a liquid in some parts of the loop 25, or it may be afluid such as carbon dioxide which reaches supercritical conditionsrather than condensing into an actual liquid.

The compressor 16 may be configured to reverse the direction of flow inthe vapor loop 25, or the engine 12 may be configured to reverse flow inthe engine coolant loop 18. The dual directions in vapor loop 25 areindicated via opposite arrows H (heating) and C (cooling). Reverse flowin either loop makes use of the separate heat exchanger 122 to conveyheat from the engine coolant loop 18 to the vapor loop 25, and then,depending on the direction of flow in the vapor loop 25, either to theair handler unit 26 (heating) or the compressor 16 and then to thethermal well 28 (air conditioning).

The vapor loop 25 may include an expansion valve 38 or an optionalelectromechanical expander and/or pump 39 as shown in phantom, alongwith any required compressor and condenser coils. Some or all of thesecomponents may reside outside of the building 11, possibly in a separateenclosure (not shown) for noise and/or environmental reasons, althoughall are components shown inside of the building 11 in FIGS. 1 and 2 forillustrative simplicity.

Optionally, a portion of the vapor loop 25 may be routed under thesurface of the ground 34 as shown. Such a routing can form the thermalwell 28. Such an option may provide for geothermal heating and coolingof the building 11, as a preferred alternative to the conventional airconditioning condenser and fan now in use for many buildings. Asunderstood in the art, the process of geothermal heating and coolingrelies on an energy exchange between air within the building 11 and theground, the latter having a relatively constant year-round temperaturebelow approximately ten feet below grade.

Thus, when temperature of the building 11 exceeds a desired temperature,heat from the building 11 can be transferred to the ground via thethermal well 28. The process works in reverse when the ambienttemperature of the building 11 is below a desired temperature, i.e.,ground heat can be used to heat the air in the building 11. Typically,the temperature of the heat sink is closer to the desired temperature ofthe building than the ambient air outside the building. Thus, use of thethermal well 28 can help optimize overall performance of the system 10.The combination of cogeneration and geothermal heating and cooling isespecially advantageous in those climates where the undergroundtemperature is below that desired for the interior temperature of thebuilding 11, so that waste heat from the engine 12 can make up thedifference. In those climates, waste heat from operating the engine 12to drive the compressor 16 for air conditioning of the building 11 canbe transferred from the engine cooling loop 18 to the vapor loop 25,such as by heat exchanger 122, to the thermal well 28. At the thermalwell 28, some of the heat will accumulate in the ground for use duringlater periods of heating, again using the vapor loop 25 and thecompressor 16.

The vapor loop 25 of FIG. 1 provides heating and cooling of the airwithin the building 11. That is, the engine 12 and MGU 14 aresufficiently sized to provide all or virtually all of the central airconditioning needs for the building 11. The compressor 16 can be run bythe engine 12 and/or by the MGU 14 as noted below, such as via selectiveactuation of one or both of a respective first and second clutch 13 and15. Heating can be done with a combination of the vapor loop 25 and heatfrom the engine cooling loop 18, e.g., when heat from the engine coolingloop 18 is not sufficient. Heating can be done with the vapor loop 25alone if using electricity from the main source 34 to power the MGU 14to drive the compressor 16 is more advantageous.

Air can be blown through heat exchangers 22 used within the enginecoolant loop 18 and the vapor loop 25. If dehumidification of thebuilding 11 is desired, the compressor 16 could be operated to cool theair, and waste heat can be added from the engine coolant loop 18 toreheat air above its dew point. The engine coolant loop 18 and the pump31 can therefore be used to provide space heating in a manner analogousto forced-air heating. Alternately, the engine 12 and the compressor 16can be used to provide space heating analogous to an electric heat pump.

When space heating is to be provided via the engine 12, the enginecoolant loop 18 extracts heat from the hot water tank 24 and carriesthis extracted heat to the air handler unit 26, whether by routing theengine coolant loop 18 through the air handler unit 26 as shown or usinga separate loop to circulate heated water from the hot water tank 24 tothe air handler unit 26. The former avoids the need for another pump,but the latter may be more efficient if it is desirable not to operatethe engine during times when heating is required. An example of thelatter is shown in FIG. 2 and discussed below.

In order to fully coordinate the various components of the cogenerationsystem 10 shown in FIG. 1, the system 10 may include a controller 50.The controller 50 is in electrical communication with the engine 12, theMGU 14, and the compressor 16. Power flow (arrow 32) occurs through thecontroller 50, or more accurately through any electrical cables andassociated power conditioning elements connected to the MGU 14 inresponse to commands from the controller 50.

Output electric power flow from the controller 50 may be provided to thebuilding 11 as indicated by arrow 30, such as to power the variouselectrical outlets, appliances, and/or machines in the building 11, andto/from the EV 40 (arrow 36) for charging a battery thereof. Thus, thecontroller 50 is configured to control the components of system 10,alone or in combination as needed, to heat and/or cool a supply of airin the building 11, to heat the water contained within the hot watertank 24, to charge the EV 40 if so configured, and to provide energy toone or more power outlets in the building 11.

The controller 50 may operate the engine 12, e.g., by controlling fueldelivery and spark/compression, monitoring oxygen sensors (not shown)associated with the catalytic converter 20, control the MGU 14 usingsolid state switches, resolvers, encoders, etc. The controller 50 canalso be configured or equipped with any required computer hardware, suchas a high-speed clock, requisite Analog-to-Digital (A/D) and/orDigital-to-Analog (D/A) circuitry, any necessary input/output circuitryand devices (I/O), as well as appropriate signal conditioning and/orbuffer circuitry. Any algorithms required by the controller 50 may bestored in memory and automatically executed to provide the requiredfunctionality.

In a particular embodiment, the cogeneration system 10 of FIG. 1 mayinclude a current sensor 60. The current sensor 60 is configured tomeasure the level of electrical current (arrow 34) being fed into and/orsupplied from the system 10 by the electrical grid, i.e., by the mainpower supply to the building 11. Grid energy may be generated viacoal-burning power plants, nuclear power plants, hydro-electric plants,etc. Depending on the supplier, some of the energy provided by the gridmay be wind-generated. Because the source of energy in the grid varieswith the supplier and/or the location of the plant generating suchenergy, the controller 50 may be programmed to monitor the mix of energyas one factor in determining how and when to control the system 10.Other possible factors include the cost of energy at different times ofday, as well as the size and energy consumption rate of the engine 12,the MGU 14, the compressor 16, and the various other components of thesystem 10.

The controller 50 of FIG. 1 thus analyzes these factors and decideswhether it is more cost advantageous to power the building 11 via energyfrom the grid, to generate all power for the building 11 via the engine12, or to use a combination of these energy sources. Optionally, thecontroller 50 may be programmed to render the cogeneration system 10“grid-neutral”. That is, the controller 50 can measure the level ofelectrical current entering the system 10 and control the components ofthe system 10 such that the current entering the system 10 issubstantially eliminated, i.e., driven to zero or as near to zero aspossible given the level of energy consumption within the building 11.Likewise, at times the system 10 may be allowed to produce excessenergy. In some markets this excess may be sold back to the grid, asindicated by the dual direction of arrow 34. The term “grid-neutral” cantherefore mean that energy is alternately used from the grid andsupplied back to the grid, with the net energy use being approximatelyzero over time.

To implement these control modes, the controller 50 may be configured tomeasure net grid power into the building 11 as well a net powergeneration by the system 10. Building load may be measured or estimatedby the difference in these two values. Instantaneous power measurementsmay be converted into a low frequency equivalent so multiple powercycles are considered when balancing power generation against loads. Thecontroller 50 may also vary the generator power factor of the MGU 14 tomodify the power factor of building 11. This can help reduce grid lossesdue to imaginary power drawn by the building 11. Where the controller 50is commanded to target a power draw (or zero power draw), themeasurements of power cab be used in a closed loop to regulate the poweroutput.

Building management control algorithms may be used by the controller 50to set the target power draw to minimize long term combination of fueland electrical costs in a target ratio, including zero net cost foreither. This can be accomplished by many methods. For instance, one mayuse finite horizon control and general predictive control, where fueland electrical costs, along with stochatic models of heat demand,electrical demand, and weather forecasts are used to minimize thedynamic optimization problem. Furthermore, the stochastic models may beadaptive and learn from long term observations of household energyusage, conversion efficiency, and storage efficiency.

The cogeneration system 10 of FIG. 1 may include optional first andsecond clutches 13 and 15, respectively. The clutches 13, 15 are incommunication with the controller 50, and may be selectively actuatedvia commands from the controller 50. In this example embodiment, theengine 12 is selectively connectable to the MGU 14 via the first clutch13, and the MGU 14 is selectively connectable to the compressor 16 viathe second clutch 15.

The controller 50 may be configured to selectively disengage the firstclutch 13 and engage the second clutch 15 to power the compressor 16 viathe MGU 14 using electrical energy from the grid, i.e., arrow 34. Thecontroller 50 can also selectively engage the first and second clutches13 and 15 so as to power the compressor 16 via the MGU 14. In thisinstance, mechanical power from the engine 12 is used when thatconfiguration is determined by the controller 50 to be the optimalchoice. Likewise, the controller 50 can selectively engage the firstclutch 13 and disengage second clutch 15 to produce electricity with theMGU 14 and heat the water contained in the water tank 24 via the engine12 without powering the compressor 16.

Battery Charging

The controller 50 may be configured to selectively disengage the firstclutch 13 and engage the second clutch 15 to power the compressor 16 viathe MGU 14 using electrical energy from the grid, i.e., arrow 34. Thecontroller 50 can also selectively engage the first and second clutches13 and 15 so as to power the compressor 16 via the MGU 14. In thisinstance, mechanical power from the engine 12 is used when thatconfiguration is determined by the controller 50 to be the optimalchoice. Likewise, the controller 50 can selectively engage the firstclutch 13 and disengage the second clutch 15 to produce electricity withthe MGU 14 and heat the water contained in the water tank 24 via theengine 12 without powering the compressor 16.

Because an EV such as the EV 40 is typically charged at night whendemand and electricity rates tend to be relatively low, charging of theEV 40 that is shown schematically in FIG. 1 can be scheduled by thecontroller 50, or by the EV 40, for charging from the grid duringoff-peak hours when heating is not required, or for charging by use ofthe engine 12 and MGU 14 when waste heat can be stored and later used.

Charging the EV 40 at night, especially during the summer, would give amore favorable choice of sources of electricity and would help to ensurethat the engine capacity of the cogeneration system 10 remains availableby day when its maximum output capacity may be needed the most, toprovide air conditioning. The controller 50 can optimize efficiencyusing delayed/off-peak charging, or by charging the EV only when heatingis required in the building 11. In this manner, the EV 40 and any airconditioning load within the building 11 can be effectively removed fromthe grid, especially during peak daytime hours, with an accompanyingreduction of CO2 emissions relative to grid charging in the conventionalmanner.

Referring to FIG. 2, certain components of the cogeneration system 10shown in FIG. 1 may be separated from the building 11 and placed aboardan EV 140 in an alternative cogeneration system 110. In this manner, afirst power plant is formed from an engine 112 and a first enginecoolant loop 118, which includes a first conductive pad or plate 70. TheEV 140 includes wheels 21 resting on the ground 34. Intake air (arrow19) is drawn into the engine 112 via an intake pipe 53, e.g., through anintake silencer 17 as noted above via an intake port 52.

A generator 62 is aboard the EV 140, with the generator 62 sending powerto a battery 56 in the form of a rechargeable energy storage system. Thebattery 56 may be selectively charged, for instance during regenerativebraking, with power flow aboard the EV 140 controlled by a powercontroller 65. An electrical line 55 and a connector 54 can be used toenable supplemental electrical power delivery to the EV 140, e.g.,connection to a charging station. Any required connections to the EV 140can be provided via an umbilical cord-type unitary connection.

The engine 112 in this particular embodiment can be used to supply heatinto the building 11. As with the cogeneration system 10 of FIG. 1, theengine 112 of system 110 discharges exhaust through a catalyticconverter 20. A muffler 75 may be used to reduce noise and filter theexhaust stream (arrow 42) as the exhaust stream 42 escapes from the EV140 to the ambient. A heat exchanger 122 as shown in phantom may bepositioned between the catalytic converter 20 and the muffler 75 totransfer heat from the exhaust to the first engine coolant loop 118.

A second engine coolant loop 218, which is part of a second power plant,is in thermal communication with the first engine coolant loop 118. Apump 332 may be used to circulate coolant through the first enginecoolant loop 118. A first conductive plate 70 of a suitable metal orother thermally conductive material may be connected to the EV 140 andpositioned under the EV 40. A similar second conductive plate 72 may bepositioned along/just under the ground 34, such that the EV 140, whenparked adjacent the building 11, brings the first conductive plate 70directly above the second conductive plate 72.

An interface 77 is thus between the conductive plates 70 and 72 with aminimal clearance as shown so as to optimize heat transfer to the secondconductive plate 72 from the first conductive plate 70. The secondengine coolant loop 218 in turn transfers heat to the hot water tank 24,with a pump 131 used in the second engine coolant loop 218 to helpcirculate coolant therein.

Within the building 11, a vapor loop 125 is in communication with theair handler unit 26 and the compressor 16 as described above, and alsowith the ambient to allow heat transfer (arrow 35) to occur with respectto the ambient. A dedicated hot water loop 27 may be used to communicateheat from the hot water tank 24 to the air handler unit 26 as analternative to extending the engine coolant loop 218 into the airhandler 26 as in the embodiment of FIG. 1. Such a loop 27 may also beused with the embodiment shown in FIG. 1., as alluded to above withreference to that Figure, as an alternative to passing the enginecoolant loop 18 through the air handler 26, as shown in FIG. 1. A pump232 may be used in the optional hot water loop 27 to circulate water tothe air handler unit 26. Air (arrows 33) enters and exits the airhandler unit 26 to accomplish heat transfer between itself and the vaporloop 125, the hot water loop 27, or both.

In this embodiment, the controller 50 within the building 11 can directelectrical energy to the building 11 (arrow 30), to the MGU 14 (arrow32), and/or to an optional storage battery 61 (arrow 37). Power from orto the grid is indicated via arrow 134. The controller 50 may be inwired or wireless electrical communication with conductive plate 72(arrow 136) so as to control the exchange of heat between the respectivefirst and second conductive plates 70 and 72. The MGU 14 does not needto function as a generator in this example, but only as a motor, becauseit is connected to the compressor 16 but not to an engine.

Referring to FIG. 3, in yet another embodiment the EV 140 may bereplaced with a non-vehicular, portable module 80 to form anothercogeneration system 210. The portable module 80 could be separate fromthe building 11 and the EV 40 of FIG. 1, which is omitted from FIG. 3for simplicity. The portable module 80 may be selectively attached tothe building 11 as shown, or to the EV 40 of FIG. 1 to provide aportable power generation/range-extending option. The latter approachmay be desirable while taking an extended trip in an EV, especiallyduring the summer months when the building 11 does not requiresubstantial heating. The portable module 80, which is merely schematicand therefore not shown to scale with respect to the building 11 in FIG.3, may be sized and shaped as needed to facilitate such use as part ofthe EV 40, to fit on a cargo rack or trailer, for example.

Connector 54, which may be electrically connected to the controller 50via a control line 71, may be used to place the portable module 80 inelectrical contact with the building 11, to provide electrical powerfrom the power controller 65 to the controller 50 and thereby to MGU 14.The cogeneration system 210 can thereby provide substantially all of thesame functions as the cogeneration system 10 shown in FIG. 1.Alternately, an inductive electrical connection (not shown) may be addedto the interface 77, either to this embodiment or to that shown in FIG.2. In the latter case, where interface 77 is between the EV 140 and thebuilding 11, an inductive electrical connection could also be used as acharging connection for the EV 140.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A cogeneration system comprising: an engine; a motor/generator unit(MGU) that is selectively powered by the engine; a compressor that isselectively powered by the engine and by the MGU; a hot water tank; anengine coolant loop which thermally connects the engine with the hotwater tank; a vapor loop which circulates refrigerant from thecompressor; an air handler unit which exchanges heat with the vaporloop; and a controller in electrical communication with the engine andthe MGU; wherein the controller is configured to control the system toheat a supply of water in the hot water tank, to selectively produceelectricity, and to heat and cool air passing through the air handlingunit.
 2. The cogeneration system of claim 1, wherein the air handlerunit also exchanges heat with the engine coolant loop.
 3. Thecogeneration system of claim 1, wherein the controller is configured touse energy from the engine to charge a high-voltage battery of anelectric vehicle having a power load of at least approximately 3 kW. 4.The cogeneration system of claim 1, further comprising first and secondclutches, wherein the engine is selectively connectable to the MGU viathe first clutch, and wherein the MGU is selectively connectable to thecompressor via the second clutch.
 5. The cogeneration system of claim 4,wherein the controller is further configured to: selectively disengagethe first clutch and engage the second clutch to power the compressorvia the MGU using electrical energy from the main power supply;selectively engage the first and second clutches to power the compressorvia the MGU using electrical energy from the engine; and selectivelydisengage the first and second clutches to heat the water in the hotwater tank via the engine without powering the compressor.
 6. Thecogeneration system of claim 1, wherein the vapor loop includes athermal well or heat sink below ground level for transferring heat withrespect to the ground.
 7. The cogeneration system of claim 1, whereinthe engine is an internal combustion engine configured to combust one ofnatural gas and propane gas.
 8. The cogeneration system of claim 1,wherein the engine is a fuel cell configured as one of a moltencarbonate fuel cell and solid oxide fuel cell.
 9. The cogenerationsystem of claim 1, further comprising a current sensor in communicationwith the controller, wherein the current sensor is configured to measurean incoming electrical current from the main power supply, and whereinthe controller is configured to control the engine and MGU so as tosubstantially eliminate the incoming electrical current.
 10. Thecogeneration system of claim 1, wherein the controller is configured todetermine which of the engine and the main power supply is the more costeffective source for powering the compressor, and to selectively powerthe MGU using the one of the engine and main power supply that is themore cost efficient source.
 11. The cogeneration system of claim 1,wherein: the engine coolant loop includes a first engine coolant loopand a second engine coolant loop; the engine and the first enginecoolant loop each reside on one of an electric vehicle and a portablemodule; and the second coolant loop is in thermal communication with thehot water tank.
 12. The cogeneration system of claim 11, furthercomprising a first conductive plate and a second conductive plate,wherein: the first conductive plate is connected to the EV or to theportable module; the first conductive plate conducts heat from theengine to the second conductive plate when the first conductive plate ispositioned adjacent to the second conductive plate; and the secondengine coolant loop conducts heat from the second conductive plate tothe hot water tank.
 13. The cogeneration system of claim 1, furthercomprising a dedicated hot water loop conveying heated water from thehot water tank to the air handler unit.
 14. A cogeneration systemcomprising: a first power plant having: an engine; and a first enginecoolant loop having a first conductive plate; and a second power plantincluding: a hot water tank; a second engine coolant loop having asecond conductive plate configured to receive heat transferred from thefirst conductive plate and to convey the received heat to the hot watertank; a motor/generator unit (MGU); a compressor; a vapor loop whichcirculates refrigerant with respect to the compressor; an air handlerunit which exchanges heat between the hot water tank and the vapor loop,and between the vapor loop and air supplied to a building powered viathe second power plant; and a controller which is configured to controlthe MGU, the compressor, and the air handler unit, alone or incombination, to thereby heat or cool at least one of a supply of airsupplied to the building and water in the hot water tank.
 15. Thecogeneration system of claim 14, wherein the first power plant ispositioned aboard one of an electric vehicle and a portable module. 16.The cogeneration system of claim 15, wherein the vapor loop forms athermal well or heat sink for storing waste heat underground.
 17. Thecogeneration system of claim 14, wherein the second power plant includesa dedicated hot water loop which conveys heated water from the hot watertank to the air handler unit.
 18. The cogeneration system of claim 14,further comprising a current sensor in communication with thecontroller, wherein the current sensor is configured to measure anincoming electrical current to the second power plant from the mainpower supply, and wherein the controller is configured to substantiallyeliminate the incoming electrical current by controlling the first powerplant.
 19. A cogeneration system including: an engine; a generator; acompressor; an air handler; a heat storage tank; a loop of a first fluidflowing through a part of the engine for transferring heat from theengine to the heat storage tank; and a loop of a second fluid whichplaces the compressor in fluid communication with the air handler;wherein: the engine is configured to operate the generator to produceelectricity while heat from the engine is accumulated in the heatstorage tank; the air handler is configured to receive heat from theheat storage tank; and the engine is configured to operate thecompressor to remove heat from the air handler unit.
 20. Thecogeneration system of claim 19, further including a controllerconnected to a main power supply, wherein: the system is configured tosupply any combination of mechanical power for the compressor andelectrical power from the generator within a mechanical power limit ofthe engine; and the system is controllable to operate without drawingpower from the main power supply unless a mechanical power limit of theengine is exceeded.